This is a 371 of PCT/JP 99/01924 filed Apr. 9, 1999.
This invention relates to an antimicrobial agent which comprises a penicillin antibiotic, in particular amoxicillin, and a cephem antibiotic, in particular cefixime or cefdinir, and which is suited for use in the prevention or treatment of respiratory infections and mixed respiratory infections. The invention is utilized in the field of medicine.
Cefixime (hereinafter sometimes referred to as xe2x80x9cCFIXxe2x80x9d) and cefdinir (hereinafter sometimes referred to as xe2x80x9cCFDNxe2x80x9d) are oral cephem antibiotics, show a broad antibacterial spectrum against gram-positive and gram-negataive bacteria, and are in wide use. However, they are not very effective against the penicillin G-resistant pneumococcus belonging to the genus Streptococcus (Streptococcus pneumoniae).
On the other hand, amoxicillin (hereinafter sometimes referred to as xe2x80x9cAMPCxe2x80x9d) is a synthetic oral penicillin, which is relatively effective against the above-mentioned pneumococcus but not so effective against gram-negative bacteria, in particular bacteria belonging to the genus Moraxella, Haemophilus or Klebsiella.
It is known that the combined use of CFIX and AMPC shows a synergistic effect against penicillin G-resistant Streptococcus pneumoniae and that said combined use is effective against mixed infection with penicillin G-resistant Streptococcus pneumoniae and Haemophilus influenzae [J. Drug Dev., 1993, 6 (Suppl. 1), 5-9].
Furthermore, it is also known that the combined use of CFDN and AMPC shows a synergistic effect against enterococcal infections (Japanese Kokai Tokkyo Koho H04-29930).
Bacteria belonging to the genus Streptococcus, Moraxella, Haemophilus or Klebsiella, for example Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae and Klebsiella pneumoniae, are main factors causative of respiratory infections. In some cases, patients are infected with only one of these bacteria and, in other cases, mixedly infected with two or more of these bacteria.
Mixed infections caused by these bacteria require urgent treatment. Since, however, a complicated procedure is required for the identification of causative bacteria, one drug having a broad antibacterial spectrum is administered prior to the identification of causative bacteria. However, among oral drugs, no one is sufficiently effective upon single drug administration. In cases where the effect is unsatisfactory, another drug is further administered in many cases after the lapse of a certain period of time.
However, by such conventional methods, it is difficult to obtain a complete cure at a stage where the symptoms of a respiratory infection are not so severe yet, so that aggravation of symptoms may result in some cases, making administration of an injection or hospitalization necessary and increasing the drug and medical expenses.
The inventors of this invention found that the combined use of a penicillin antibiotic, in particular AMPC, and a cephem antibiotic, in particular CFIX or CFDN, shows a synergistic effect against not only single infections but also mixed infections with the bacteria mentioned above and said combined use provides an antimicrobial agent useful in the prevention and treatment of respiratory infections with one bacterial species and of mixed respiratory infections with a plurality of bacteria.